Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
  • C09C3/006—Combinations of treatments provided for in groups C09C3/04 - C09C3/12
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0081—Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/28—Compounds of silicon
  • C09C1/30—Silicic acid
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/28—Compounds of silicon
  • C09C1/30—Silicic acid
  • C09C1/3009—Physical treatment, e.g. grinding; treatment with ultrasonic vibrations
  • C09C1/3036—Agglomeration, granulation, pelleting
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/50—Agglomerated particles
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/14—Pore volume
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/16—Pore diameter
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/16—Pore diameter
  • C01P2006/17—Pore diameter distribution

Definitions

• This invention relates to aggregates of particles of which a portion of the particles is of silicon dioxide and to elastomers reinforced therewith.
• the invention relates to tires having rubber treads which are composed of such reinforced elastomers.
• Silica which is primarily composed of silicon dioxide, is often used to reinforce various elastomers, particularly when used in conjunction with a silica coupling agent, or silica coupler.
• the silica or silicon dioxide which is its major constituent, is typically used in the form of an aggregate of the fine silica particles which are bonded together due primarily to the manner in which they are prepared, particularly when the silica is prepared by a precipitation process.
• the primary silica particles are typically sufficiently bonded together so that even upon application of a relatively high shear mixing of silica/rubber mixtures, at least a portion of the aggregate structure remains and the aggregate is not completely broken down to its ultimate primary silica particles. This phenomenon is considered herein to be known to those skilled in the silica/rubber mixing art.
• silica typically used for rubber reinforcement purposes while referred to as “silica”, it might be more appropriately referred to as aggregates of silica particles.
• the invention also relates to tires having rubber treads which are composed of elastomers which are reinforced with aggregates of silica particles of which at least a portion of the particles are of silicon dioxide.
• Various rubber products including tires and industrial products, are composed of elastomers, or blends of elastomers, which are conventionally reinforced with reinforcing particulate fillers to enhance their physical properties.
• silica is also sometimes solely used or, alternatively, is used in conjunction with carbon black to reinforce the elastomers and/or to otherwise enhance their physical properties.
• carbon black and/or silica to reinforce elastomers is well known to those having skill in such art.
• Such silica is normally composed primarily of silicon dioxide which contains silanol groups on its surface as well as water of adsorption unless it is used in a dried or dehydrated form. While the silica can be, for example, of the pyrogenic or precipitated type, the precipitated silica is used in most applications.
• the silica particularly precipitated silica, is generally considered to be in the form of aggregates of silica particles.
• silica as may be referred to herein, is generally intended to mean aggregates of silica particles unless the primary silica particles are referenced.
• silica coupler in order to enhance the elastomer reinforcing effect of silica, a coupling agent, or silica coupler, is often used in conjunction with the silica.
• silica coupler is often composed of a moiety which is reactive towards the silanol groups present on the silicon dioxide surface and/or towards Si-O-Si groups, or any other active sites, such as, for example, an organosilane, and of a moiety which is reactive with the carbon-to-carbon double bonds of the elastomer such as, for example, a polysulfide or a mercaptan.
• silica coupler with one moiety reacted with the silica and one moiety reacted with the elastomer, then couples, or connects, the silica to the rubber in a manner which enables the silica to more effectively reinforce the rubber.
• Such use of silica couplers is considered to be well known to those having a skill in the silica reinforcement of rubber art.
• coupling agents are taught for use in combining silica and rubber, such as for example, silane coupling agents which contain a polysulfide component, or structure, such as bis-(3-triethoxysilylpropyl) tetrasulfide.
• Such coupling agent has a silane moiety which is reactive with silicon dioxide of the silica and a tetrasulfide moiety which is reactive with carbon-to-carbon double bonds of a sulfur curable elastomer.
• Dithiodipropionic acid for example, may also be considered for use as a silica coupling agent either individually or, for example, in combination with the aforesaid silane tetrasulfide coupling agent.
• Pneumatic rubber tires are conventionally prepared with a rubber tread which can be a blend of various rubbers, or elastomers, which may be reinforced with carbon black, silica or mixtures or carbon black and silica.
• tire treads Rubbers are conventionally evaluated, selected and blended for a purpose of achieving desired tire tread properties and particularly a balance of tire tread characteristic properties, mainly, rolling resistance, traction and wear.
• the elastomer reinforcing ability of aggregates of silicon dioxide is often considered to be due to the size and shape of the aggregates, their surface activity and porosity as well as various chemical and physical interactions of the silica aggregates with silica couplers and/or elastomers.
• silica aggregates tend to be different among the various types of silica aggregates which can result in substantial variations in silica reinforced elastomer processing, prior to sulfur vulcanization of the elastomer, as well as properties of vulcanized silica reinforced elastomers. Such phenomena are well known to those having skill in the silica reinforced rubber art.
• silica aggregates used for tire tread elastomer reinforcement is, for example, evidenced by a difficulty providing a silica reinforced elastomer for a tire tread which will demonstrate a suitable balance between tread wear, rolling resistance and traction properties for the tire.
• silica aggregates used in elastomer reinforcement are sometimes observed to be difficult to disperse sufficiently homogeneously or sufficiently efficiently within the elastomer to provide a silica reinforced elastomer for a tire tread having a suitable balance between treadwear, rolling resistance and traction for a tire.
• Silicas are typically produced by one of three processes and are generally referred to by the general process in which they are produced, namely pyrogenic, gel and precipitated silicas. For elastomer reinforcement, precipitated silicas are usually preferred.
• Pyrogenic or fumed silicas may be produced, for example, by a vapor process in which silicon tetrachloride vapor is reacted with oxygen and hydrogen at elevated temperatures.
• Silica gels which may be, for example, hydrogels, xerogels or aerogels, may be produced by reacting a soluble silicate such as sodium silicate with a strong sulfuric acid. The resulting gel is washed to remove residual salt, dried and then usually micronized by steam treatment to form a hydrogel. Aerogels may be similarly produced except that the water of the gel is replaced by an alcohol following which the gel is heated to remove the alcohol under super critical drying conditions (high pressure and high temperature into an autoclave) Contrary to aerogels, xerogels are not dried under super critical conditions. They are indeed inorganic hydrated oxide precipitated from an aqueous solution and dried in air or under a vacuum.
• Precipitated silicas may be produced, for example, by forming a soluble silicate by reacting particles of silicon dioxide (eg: sand) with a strong base, such as sodium hydroxide, to form after dissolution an aqueous silicate solution; followed by destabilizing the silicate solution by addition of an organic or mineral acid and/or acidifying gas such as carbon dioxide to change the pH of the mixture and cause a reaction to take place from which the silica is precipitated, substantially in the form of fine particles of silicon dioxide which may be in the aforesaid aggregate form and may appear in a gel-like form.
• silicon dioxide eg: sand
• a strong base such as sodium hydroxide
• the resulting slurry, or gel is conventionally filtered and washed with water to remove the reaction by-product, which is the alkali metal salt of the acidification agent.
• the filter cake is then typically dried to yield a silica of desired aggregate particle size.
• the precipitation process involving, for example, sequential and/or intermittent additions of the silicate solution and/or acid, control of the pH, optionally stopping the acid addition and ageing of the mixture prior to resuming acid addition to reach the desired pH, ageing the gel or filter cake prior to washing with water which might sometimes be called post ageing and variations of various process temperatures and times.
• a process of producing a silica may be found, for example, in European Patent publication EP-A1-170579.
• the physical characterizations of the precipitated silicas namely the aggregates thereof, can vary considerably as well as their use as reinforcement for elastomer(s) and resulting elastomer properties according to the selection of silicate reaction materials and reaction conditions.
• an aggregate of particles for the reinforcement of elastomers which are somewhat similar to aggregates of silica particles except that a portion of the silicon present in the silicon dioxide particles has been replaced with other atoms and, further, that functional groups and/or polymers have been grafted to the silica surface and/or that the aggregate has been treated with a surfactant.
• a process of producing an aggregate of particles comprises the steps of:
• step (A) the strong base is reacted with the aforesaid inorganic materials and a water solution is prepared of the product thereof.
• the strong base can be in a form of an aqueous solution thereof, thereby, in accordance with step (A), reacting the inorganic materials in the presence of water with the strong base to form the water solution of the product thereof.
• the surfactant may be of a commercially available type, including for example, alkylbenzene sulfonate, alcohol sulfate, alcohol ether sulfate, alcohol ethoxylate, alkylphenol ethoxylates, fatty acid alkanolamines, or fatty acid amine oxides.
• the aluminum, iron, magnesium, boron, titanium, zirconium, vanadium, niobium and phosphorus can be introduced as, for example, as oxide or salt thereof, so long as the requirement that the reaction thereof, in the presence of water, with a strong base produces a aqueous solution of a product thereof.
• Representative examples are salts selected from at least one of carbonate, silicate, aluminate, borate, alumino-silicate, phosphate, sulfate, halogenide either pure or in the hydrogenated form, e.g. NaHSO4, KH2PO4, Na2H2SiO4, etc.
• Combinations of the salts or mixed salts may also be used.
• the cation of the salt is considered herein to be also of some importance and may be of any suitable element and is more preferably selected from the alkali or earth alkaline group of the periodic system such as, for example, Na, K, Ca, Mg, Li; others could be Zr, Fe, etc. to preferably produce a water soluble salt thereof upon addition of sodium hydroxide.
• representative examples of such salts are iron sulfate, magnesium sulfate, calcium chloride, potassium phosphate, zirconium sulfate, titanium dioxide and zinc oxide.
• the grafting of functional groups onto one or more particles of the aggregate may be accomplished through chemical bonding between any coupling agent described in the literature for SiO2 and reinforcing filler which will provide the functional groups.
• any coupling agent described in the literature for SiO2 and reinforcing filler which will provide the functional groups are of types X-R-Z or (X-R-Z)2.
• (X-R-Z)2 is a symmetrical molecule e.g.
• Z may also be an unsaturated radical as described in standard textbooks, representative materials of which are, for example, allyl radicals having from 4 to 10 carbon atoms, vinyl radicals having from 4 to 10 carbon atoms, acryl radicals having from 8 to 30 carbon atoms, aryl radicals having from 8 to 30 carbon atoms, pyridyl radicals having from 8 to 30 carbon atoms and piperidine radicals in which x is an integer of from 1 to 8, preferably from 3 to 6.
• the size and shape of the primary particles which can be round or jagged, and that the size distribution of the primary particles as well as of the aggregates and of the pores are as important as the types and amounts of functional groups attached to the surface of the primary particles.
• Such properties of the primary particles and aggregates thereof are considered herein to be suitably obtained by control of the materials utilized, the process of precipitation and the drying process.
• the aggregates may be used as reinforcing filler for various solution polymerization prepared as well as emulsion polymerization prepared diene based elastomers such as, for example, cis 1,4-polyisoprene rubber - natural and synthetic, cis 1,4-polybutadiene rubber, styrene/butadiene copolymer rubber, butadiene/isobutylene copolymer rubber, EPDM rubber, Styrene/isoprene/butadiene terpolymer rubber, butadiene/acrylonitrile rubber, 3,4-polyisoprene rubber and isoprene/butadiene copolymer rubber.
• cis 1,4-polyisoprene rubber - natural and synthetic such as, cis 1,4-polybutadiene rubber, styrene/butadiene copolymer rubber, butadiene/isobutylene copolymer rubber, EPDM rubber,
• a rubber composition, and tire having a rubber tread comprised of such composition is provided which is comprised of (A) 100 parts by weight of at least one diene based elastomer, (B) about 5 to about 100, optionally about 60 to about 90, parts by weight of an aggregate of this invention and (C) a silica coupler having a moiety reactive with silicon dioxide and a moiety reactive with the said elastomer, which might be generally be thought as being reactive with the carbon-to-carbon double bonds of the elastomer.
• the aggregate produced by the described methods is hygroscopic and sensitive to water and humidity. It is normally recommended, especially where the dried surface of the aggregate (particles) is treated by surfactant(s), that the aggregates be packed in sealed, weighed, bags for prevention of contamination by water, humidity and/or other material from the environment. Such protected aggregates are considered herein to provide good dispersion, reactivity and stability for use in the reinforcement of elastomers.
• the aggregate have at least one of the following physical parameters to be suitable for use as reinforcement for elastomers:
• the aggregates of this invention may also be, in general, typically characterized by having a projected area of the silica aggregates ranging between 1,000 and 20,000 x 10 ⁇ 18m2 and preferably about 2000 to about 10,000 x 10 ⁇ 18 m2).
• the projected area of an aggregate can be determined, in general, by ASTM test No. D3849.
• a transmission electron microscope can be used, with a magnification of 150,000x at 120 kilovolts, coupled with an on-line image analyzer.
• Sample preparation is considered important.
• a sample can be prepared by the steps of dispersing 10 mg of aggregate in a 30 ml mixture of 10 ml of water and 20 ml isopropyl alcohol in a glass beaker of 250 ml capacity, for example.
• the beaker is positioned within the ultrasonic device and operated at a temperature of about 25°C., a frequency of about 55 kHz and an energy level of about 100 W for 1 hour.
• the Formvar grid is obtained from Balzers as item number BU-006-034-T.
• the projected area is typically determined as an average of least 2,000, preferably at least 8,000, aggregates and reported in terms of square meters (for example, 10 ⁇ 18 m2.
• the percentage of the CTAB surface area of the aggregate which has reacted with the substituent should be from about 1 to about 100, and preferably from 2 to 50 percent.
• the detergent content should be comprised from about 0.1 to about 50, preferably about 2 to about 20 percent of the silica weight. In this manner, it is considered herein that the associated water of absorption on the surface of the aggregate is somewhat replaced by the detergent.
• the density of the aggregates of this invention is considered herein to be typically in a range of about 0.1 to about 3.0 g/cm3. It is considered herein that very low density aggregates are beneficial to reduce somewhat significantly the weight of aggregate reinforced elastomers which can be an important consideration in various manufactured products such as for example rubber tires, including the treads of tires.
• a pneumatic tire having a tread comprised of (A) 100 parts by weight of at least one diene based elastomer, (B) about 5 to about 100, optionally about 30 to about 90, phr of an aggregate material which is a material comprised of about 50 to about 100, preferably 100, weight percent of the aggregate of this invention and correspondingly, about zero to about 50 weight percent silica, (C) at least one silica coupler having a moiety reactive with silicon dioxide and a moiety reactive with said elastomer, in a weight ratio of aggregate and silica, if silica is used, to coupler of about 7/1 to about 15/1, and (D) about 0 to about 80, optionally up to about 30, and optionally about 5 to about 30, phr carbon black, wherein the weight ratio of aggregate and silica, if silica is used, to carbon black, where carbon black is used, is at least about 0.1/1, optionally at least about 3/1,
• silicas may also be mixed with the aggregates of this invention for the reinforcement of the diene based elastomers.
• Such silicas are typically characterized by the aforesaid BET and CTAB surface areas.
• Representative of such silicas for example, only and without limitation, are silicas available from PPG Industries under the Hi-Sil trademark with designations 210, 243, etc; silicas available from Rhone-Poulenc, with designations of Z1165MP and Z165GR, silicas available from Degussa AG with designations VN2 and VN3, and silicas available from AKZO Chemie, etc.
• the aggregate material of the (B) component of the tire tread is a material which consists essentially of the aggregate of this invention.
• the aggregate may contain a very minor amount of silica (eg. less than about 10 percent by weight), it is primarily and essentially, or practically, about 100 percent of the aggregate of this invention.
• the rubber composition of the tread rubber would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black.
• curing aids such as sulfur, activators, retarders and accelerators
• processing additives such as oils, resins including tackifying resins, silicas, and plasticizers
• fillers pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants
• peptizing agents and reinforcing materials such as, for example, carbon black.
• the additives mentioned above are selected and commonly used in conventional amounts.
• the tires can be built, shaped, molded and cured by various methods which will be readily apparent to those having skill in such art.

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Cited By (36)

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Citations (5)

• 1993
  • 1993-09-08 CA CA 2105719 patent/CA2105719A1/en not_active Abandoned
• 1994
  • 1994-06-20 EP EP94109496A patent/EP0631982B1/de not_active Expired - Lifetime
  • 1994-06-20 DE DE1994629597 patent/DE69429597T2/de not_active Expired - Fee Related

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